P H O T O G R A M M E T RY
The circular photographic image produced by the Fisheye-Nikkor 6mm f/2.8 is an exact reproduction on a flat plane of all objects within the 220° field. This feature enables the lens to be used in locating astral bodies or recording cloud distribution. The center of the image corresponds to the zenith in the angle of view, and the distance of any point in the image from this center is directly proportional to its angle from the zenith, expressed by the equation y = CO, where y is the distance of the point from the image center, 6 is the zenith angle, and C is a constant (see below). For example, a point j n the image 4mm from the center represents an object at an angle of 37.2 from the zenith in the angle of view. The table below gives zenith angles for points at given distances from the center of the film image.
Relation of Zenith Angle to Distance of Point from Image Center
6: Zenith angle
y : Distance of point from image center
y 8° A0°
0.00.000
0.5 4.615 4.615
1.0 9.241 4.626
1.5 13.873 4.632
2.0 18.514 4.641
2.5 23.165 4.651
3.0 27.829 4.664
3.5 32.510 4.681
4.0 37.210 4.700
4.5 41.929 4.719
5.0 46.669 4.740
5.5 51.431 4.762
6.0 56.214 4.783
6.5 61.019 4.805
7.0 65.845 4.826
7.5 70.690 4.845
8.0 75.553 4.863
8.5 80.429 4.876
9.0 85.317 4.888
9.5 90.216 4.899
10.0 95.129 4.913
10.5 100.069 4.940
11.0 105.061 4.992
11.5 110.155 5.094
